I don’t like the
cheap so called ‘drop-in’
lithium batteries with built-in BMS. I prefer to be able to measure each cells voltage to check what’s happening. I also like to have a replaceable BMS and relay rather than have it sealed within
battery. The internal mosfet type relay cannot carry the same
current as a mechanical contractor and that is why the charge/discharge currents are so low. If several of these
cheap lithium batteries are paralleled to provide the
current required for a big
inverter you create a few extra problems. If for any reason one of the batteries BMS trips, all the current has to be provided by the remaining batteries which further loads up the remaining relays.
My Winstone
LiFePo4 cells on the
boat are now over 9 years old and still perform great. I have just put a set of CALB cells with external Zeva BMS in the camper. I tried solid state relays with this new
installation and have now gone through two relays under warranty. They cannot handle the loads. I am reverting back to the old style contactor. If it was integrated in the sealed
battery then the whole battery would have to be replaced.
In my opinion individual cells with external BMS & relay is the way to go.